1. Field of the Invention
The present invention relates to an exposure controlling apparatus for cameras, and more particularly, it relates to an exposure controlling apparatus for a camera, wherein a divided photometry mode or a central portion photometry mode can be selected.
2. Related Background Art
A conventional exposure controlling apparatus of a camera is provided with a photometry means arranged in a camera finder, which photometry means measures incident luminous flux introduced into the camera through a taking lens and permits a divided photometry (i.e., a so-called multi-pattern photometry) for performing photometry regarding an object field (picture) by dividing the field into at least a central portion and a peripheral portion, and a central portion photometry for performing photometry regarding the central portion of the field, whereby an operator can select the divided photometry mode or the central portion photometry mode freely by means of an external selection means.
For example, it has been proposed to divide the object field into five areas, one of which is a central portion area of the field and the others of which correspond to four areas obtained by dividing a peripheral portion encircling the central portion, and to employ five photometry light receiving devices arranged in a mosaic pattern. If such photometry light receiving devices are arranged, for example, in a finder of a single lens reflex camera in which taking lenses can be changed, depending upon the positionswhere the photometry light receiving devices are arranged, when the full aperture F value is large, the amount of light from the peripheral portion of the field to the photometry light receiving devices will be insufficient. As a result, in the divided photometry mode which uses the whole object field in photometry, a correct or optimum exposure value cannot be obtained.
Accordingly, in a camera wherein the divided photometry mode and the central portion photometry mode can be selected, if the divided photometry mode is selected in such a camera including a taking lens having a large full-aperture F value (i.e., a full-aperture diameter is small), the optimum exposure cannot be obtained. This is particularly so tendency will be seen strongly when a bright focusing plate having strong orientation is used with the camera as in a recent case.
Further, in a conventional technique wherein the photometry modes can be changed over by means of the external selection means as mentioned above, since the operator can select the divided photometry mode or the central portion photometry mode optionally, if he selects the divided photometry mode in a camera including a taking lens which is a dark super telephoto lens having a large full-aperture F value, the following problem will arise. That is to say, since the lens is dark, the luminous flux from the object field cannot be introduced into the peripheries of the light receiving surfaces of the photometry means due to vignetting of the lens, so that the optimum exposure cannot be attained, with the result that the value of the exposure will be insufficient for the divided photometry.